ES2226799T3 - CURABLE SILICONE RUBBER COMPOSITIONS WITH AN IMPROVED FLAME RESISTANCE. - Google Patents

Abstract

A curable silicone wire and cable coating composition with improved flame resistance at heat flux rates of 50 to 90 kW/m2, made by mixing ingredients comprises:(A) 30 to 90 weight percent of a heat-curable non-halogenated organosiloxane polymer, containing at least 2 alkenyl groups per molecule,(B) 1 to 65 weight percent of a reinforcing silica filler, based on the total composition,(C) 5 to 70 weight percent wollastonite having an average particle size of 2 to 30 mum, based on the total composition, and(D) curing component sufficient to cure the composition.

Description

Compositions of curable silicone rubber with an improved flame resistance.

This invention relates to compositions of Curable silicone rubber with improved flame resistance. More specifically, this invention relates to rubber of silicone for use as insulation materials and Overpressure transmission cable sheathing. Wires  overpressure transmission show low flame spread and low smoke generation properties, acceptable by industrial standards Also, because these compositions do not  contain halogens, their combustion byproducts are expected Be less toxic and corrosive.

Background of the invention

In the construction of numerous buildings, it place a suspended ceiling under the structural floor panel It is constructed of concrete for example. The accessories of lighting as well as other elements appear under the roof discontinued.

The space between the roof and the structural floor of which it is suspended, serves as an impending air chamber of return for heating system elements and cooling as well as convenient location for installation of communication cables, including data cables and signals for use in telephone systems, IT, control, alarm and associated systems. It's nothing weird that these impending chambers are continuous throughout the length and width of each floor.

Also, the space below a floor grown in a computer room, it is considered as a camera imperative if connected to a conduit or a camera imperative

As a general rule, the National Electrical Code (NEC) requires that the cables in the impending chambers be enclosed in metal ducts. However, the NEC allows any exception to this requirement as long as these cables are tested and certified by a test agent independent as the Underwriters Laboratories (UL) in which they have adequate characteristics of low flame spread and smoke production

The flame propagation and smoke production of the cable are measured by using UL 910, Standard Test Method for the Fire and Smoke characteristics of the Electric and Fiber Optic Cables used in the Air Handling Spaces. The UL 910 test, also known by NFPA 262 test, is considered to be the most severe performance test. Hirshler in his "Analysis of and Potential Correlations Between Fire Tests for Electrical Cables, and How to Use This Information for Fire Hazard Assessment", Fire Technology, Vol. 33, No. 4 (1977) describes several tests used in electrical cables for evaluate fire hazards, and is incorporated here as a reference for test information. The Steiner tunnel test is quite severe because it combines a high heat flow with a long duration. Normally, thermoplastic materials such as polyvinyl chloride (PVC) with high load and fluoro-polymers, such as FEP, pass the Steiner tunnel test.

However, the materials of Fluoro-polymer are somewhat difficult to process. Also, some of the materials containing fluorine have a relatively high dielectric constant which makes them Unattractive to the media.

In addition, PVC and Fluoro-polymers such as FEP are materials halogenated There has been a desire to overcome some problems that exist with respect to the use of halogenated materials like fluoro-polymers and chloride polyvinyl (PVC). These materials show unwanted levels of corrosion in fires. If a Fluoro-polymer, hydrogen fluoride is formed under the influence of heat, which causes corrosion. For him PVC, hydrogen chloride is formed.

Silicones, especially non-halogenated polydimethyl siloxanes, are known for their resistance to fire and heat. It has been shown that the silicones burned in a cone calorimeter had comparatively a low maximum heat release rate, a total heat released, an average carbon monoxide production rate, and an average smoke production rate compared to the organic compound See, for example, Fu-Yu Hshieh and Robert R. Buch, "Controlled-atmosphere Cone Calorimeter, Intermediate-scale Calorimeter, and Cone Corrosimeter Studies of Silicones", Proc. Int. Conf. Fire Safety, Vol. 23, p 213-239 (1977). Silicone rubber compositions as a coating for wire and cable applications are also known, and are generally less expensive than fluoro-polymers. However, silicone rubber formulations did not previously pass the UL 910 test, and are not currently qualified for use in overpressure chambers. Silicones, for example, are not currently listed in the UL 1581 specification for wiring materials. It is believed that this is due in part to the poor formation of coal due to its exposure to high thermal flow rates. The surface of many silicone rubber compositions used for cable sheathing disintegrates when burned, exposing the unburned polymer and substrate, allowing the flame to spread. Due to these characteristics, no silicone is currently qualified for use in overpressure cable sheathing. The ability to use a non-halogenated polydimethyl siloxane composition as an overpressure cable sheath would offer a non-corrosive material, less expensive than fluoro-polymers.

Recently, Sawada, in the patent application Japanese 9-55125 described an electric cable Fire retardant that had excellent fire resistance. It forms a 0.1-1.0 mm thick flame retardant layer by means of extrusion of a coating composition that is of 200-500 parts by weight of four fillings inorganic with respect to 100 parts by weight of silicone rubber hot vulcanized. The four fillings are made of glass, alumina, wollastonite, and mica. Sawada proves that they must be present the four fillers for sufficient strength to the fire The silicone rubber used by Sawada is hot vulcanized, and may also contain an agent of cross-linking composed of an organic peroxide, but not Specify no information on the chemistry of silicone. He Glass powder is made up of particles that have a diameter of 50-300 µm and the glass content is 50 to 125 wet parts per 100 parts by weight of silicone rubber  hot vulcanized. The alumina that is used, is composed of particles having a diameter of 50-200 µm, and alumina content is in the range of 50 to 125 parts by weight per 100 parts by weight of silicone rubber hot vulcanized. Wollastonite is used in the form of crystals in anhydrous calcium silicate needles with a size of 100-300 particles. Content wollastonite is 50 to 125 parts by weight per 100 parts in Hot vulcanized silicone rubber weight. Mica preferably it has a lamellar shape with a relationship between dimensions of approximately 30-70 and a size of 100-300 particles. Mica content is 50-125 parts by weight per 100 parts in Hot vulcanized silicone rubber weight. He Sawada wire coating was tested according to the Fire Services and Fire Resistance Test Act. The test was performed following a flame curve with a temperature of 840 ° C for a 30 min burn process.

Summary of the invention

The invention is a rubber composition of curable silicone with improved flame resistance to thermal flow rates of 50 to 90 kW. More way specifically, the invention is a coating composition of silicone rubber cable and wire capable of passing the UL 910 test when it extends over the transmission cable means. He inventor has discovered that some rubber compositions of curable silicone containing 5 to 70 percent by weight of wollastonite, which have a relationship between dimensions of at least 3 to 1, and having an average particle size of 2 to 30 µm, they have surprisingly good fire resistance and form hard coals when burned. The coating composition is suitable for a flame resistant coating layer over a cable, thread or fiber used in the construction of a camera to overpressure

Description of the drawings

Figure 1 shows the detachment data of heat (HRR) as a function of time for five liquid samples of silicone rubber that were cured in test plates and burned in a cone calorimeter at 50 kW / m2. Each of the Silicone samples were formulated by using a inorganic filler other than 10 percent by volume, based on the sample. Sample 1-1 was formulated with earth from diatoms Sample 1-2 was formulated with wollastonite Sample 1-3 was formulated with calcium carbonate Sample 1-4 was formulated with aluminum oxide. Sample 1-5 was formulated with smoked silica Sample 1-6 was composed without filling for comparison with samples filled.

Figure 2 shows the detachment data of heat (HRR) as a function of time for two liquid samples of silicone rubber that was cured in test plates and burned in a cone calorimeter at 88 kW / m2. Each of the samples Silicone was formulated with 38.7% inorganic filler. He Inorganic filler of Sample 2-1 was wollastonite The inorganic filling of the Sample 2-2 was diatomaceous earth.

Figure 3 shows the detachment data Heat (HRR) as a function of time for three rubber samples of silicone of great consistency that were cured in plates of test and burned in a cone calorimeter at 88 kW / m2. Every one of the silicone samples was formulated with approximately the 8.0 percent by weight of amorphous silica and 60.0 percent by weight of a second inorganic filler. In Sample 3-1 the second inorganic filler was diatomaceous earth. In the Sample 3-2 the second inorganic filler was wollastonite. In Sample 3-3 the second inorganic filler was a mixture composed of 50 percent by weight of land of diatoms and 50 percent by weight wollastonite.

Figure 4 shows the detachment data of heat (HRR) as a function of time for two rubber samples of high consistency silicone that were cured in test plates and burned in a cone calorimeter at 88 kW / m2. Each of The silicone samples were formulated with approximately 8.0 per percent by weight of amorphous silica and 60.0 percent by weight of wollastonite In Sample 4-1 the degree of wollastonite had an average particle size of 12 µm and a particle size in the range of 1-393 um, and a ratio between dimensions of 20: 1. In the Sample 4-2 the grade of wollastonite had a size average of 10 µm and a particle size in the range of 1-110 µm and a relationship between dimensions of 17: 1.

Figure 5 shows the detachment data of heat (HRR) as a function of time for two rubber samples of high consistency silicone that were cured in test plates and burned in a cone calorimeter at 50 kW / m2. The sample 5-1 did not contain any platinum complex as smoke reduction agent. Sample 5-2 It contained 0.5 percent by weight of a platinum complex.

Figure 6 shows the detachment data of heat (HRR) as a function of time for two liquid samples of silicone rubber that was cured in test plates and burned in a cone calorimeter at 50 kW / m2. Each of the samples it was formulated with approximately 10 percent by volume of inorganic filler Sample 6-1 was formulated with synthetic calcium silicate. Sample 6-2 is formulated with wollastonite.

Detailed description of the invention

This invention is a silicone composition. curable coating of wires and cables with a resistance flame enhanced at thermal flow rates of 50 to 90 kW / m2, made by mixing ingredients that include:

(TO)

of the 30 to 90 percent by weight of a polymer of thermosetting non-halogenated organo-siloxane, which It contains at least 2 alkenyl groups per molecule,

(B)

of the 1 to 65 percent by weight of a reinforcing silica filler, based on the total composition,

(C)

of the 5 to 70 weight percent wollastonite that has a size average of particles of 2 to 30 µm, based on the composition total, and

(D)

he sufficient healing component to cure the composition.

This invention also includes a camera cable. overpressure for transmission media comprising a silicone rubber coating formed by the coating and The healing of the previous composition.

Component A, the polymer of organo-siloxane has the average composition of R a SiO (4-a) / 2. In the formula, R is selected from the monovalent hydrocarbon groups substituted and unsubstituted and exemplified by the groups of alkyl such as methyl, ethyl, and propyl; alkenyl groups such as vinyl, allyl, butenyl and hexenyl; aryl groups like the phenyl; and aryl-alkyls like the 2-phenyl ethyl. The subscript a is a value from 1.95 to 2.05.

The organosiloxane polymer it has at least 2 alkenyl groups bonded with silicon in each molecule. Alkenyl groups can be linked in positions pending, in terminal positions, or in both positions. The polymer molecular structure of organo-siloxane generally has a degree of polymerization (dp) in the range of 200 to 20,000. This dp range includes polymers that are thick liquids, fluids as well as those with a thick consistency, similar to rubber. Typically, silicone rubber compositions used in wire and cable applications routinely use the polymers with a thick consistency, similar to rubber for process them more easily in screw type extruders. Generally, these thick polymers, similar to rubber, have a dp above 1500 approximately and have a number of Williams plasticity (ASTM D926) in the range of approximately 30 to 250 and preferably 95 to 125. The plasticity number, as used here, it is defined as being the thickness in mm x 100 of a cylindrical test tube of 2 cubic cm in volume and approximately 10 mm high after submitting the test tube at a compressive load of 49 Newtons for three minutes at 25 ° C More recently, it has been discovered that rubber silicone made from polymers that are fluid fluids Thick was useful as a material for wires and cables. These materials can typically be pumped through a nozzle to line the wire or cable without using an extruder of the type of screw. How less effort is needed to process these materials, may be more suitable for coating cables of fiberglass or polymer. Polymers that are liquid thick fluids have a dp below approximately 1500 and they have a viscosity between 200 and 100,000 mPa.s at 25 ° C.

The organosiloxane polymer it can be a homopolymer or a copolymer or a mixture of these polymers The siloxyl units comprising the polymer of organo-siloxane are exemplified by the dimethyl siloxy, vinyl methyl siloxy and methyl phenyl siloxy. The groups molecular molecules in the polymer of organo-siloxane are exemplified by the groups of trimethyl-siloxy, and of vinyl dimethyl siloxy. Polymer of organo-siloxane is exemplified by the copolymer from dimethyl-siloxane-vinyl-methyl-siloxane locked at its end by vinyl dimethyl siloxy, polydimethyl-siloxane blocked at its end by vinyl dimethyl siloxy, the copolymer of dimethyl-siloxane-vinyl-methyl-siloxane locked at its end by vinyl methyl hydroxy siloxy, and the dimethyl siloxane copolymer / methyl phenyl siloxane / vinyl-methyl-siloxane blocked in its extreme by vinyl dimethyl siloxy.

Component B is a silica filler of reinforcement, to provide mechanical properties increased in the present silicone rubber composition thermosetting The filler can be any silica filler, treated or untreated, which is known to reinforce the polydiorgano-siloxane and that is selected preferably from finely divided, smoked forms  and precipitates of silica and silica aerogels that have a surface area of at least approximately 50 m 2 / g, and preferably from 150 to 400 m2 / g. The filling is added typically at a level of approximately 1 to 65 percent in weight of the weight of the total composition, and preferably in a range of 5 to 25 percent by weight of the total composition.

It is preferred to treat the silica filler of reinforcement so that its surface becomes hydrophobic, as it is typically implemented in the art of silicone rubber. This can be done by reacting the silica filler of reinforcement with a liquid organo-silicic compound containing silanol groups or hydrolyzable precursors of silanol groups.

The compounds usable as agents of treatment of fillers, also called anti-pleating agents or plasticizers in the art of silicone rubber, include these ingredients such as polydiorgano-siloxanes low molecular weight liquids terminated by hydroxyl or alkoxy, including α, var varpi-silane diols, hexa-organo-disiloxanes, cyclodimethyl siloxanes and hexa-organo-disilazannos.

Component (C) is 5 to 70 percent in wollastonite weight that has an average particle size of 2 to 30 µm. Wollastonite, also known as metasilicate calcium, is a mineral that occurs naturally. Wollastonite used in this invention is a mined form, which has a acicular morphology, that is, a needle-like shape. Typically, this mineral has a relationship between dimensions of 3: 1 or greater. It is preferred that the wollastonite have a size average of particles approximately 5 to 15 µm and a dimension ratio greater than about 15: 1. The wollastonite used in this invention has a low zone BET surface, typically less than 25 m 2 / g, and preferably less than 5 m 2 / g. The compositions that they use calcium silicates of different forms and morphologies that the wollastonite, do not show the formation of coal or the casualties heat release rates of those herein invention.

For example, a composition made with calcium synthetic, which typically has a spherical shape, demonstrates in the examples below do not have the functional characteristics desired flame retardants. A preferred wollastonite is supplied by NICO® Minerals, Inc., Willsboro NY. Compositions with less than approximately 5 percent by weight of wollastonite do not show the formation of coal and the low rate of detachment of heat of the present invention.

The upper limit of wollastonite that is useful will depend on the desired properties in the cured composition and not cured Generally, wollastonite present in more than approximately 70 percent by weight results in compositions uncured that are too thick and therefore difficult to process, and results in cured compositions that have a reduced tensile strength and elongation.

The healing component (D) can be any of the healing components well known in the art of the silicone elastomer. For example, the compositions of Curable silicone elastomer of this invention can be cured to the elastomeric state by exposure to the beams electronic, ultraviolet rays, electromagnetic waves, or the heat When heat is used as a healing mechanism, an organic peroxide curing agent can be used. The Examples of suitable organic peroxide curing agents include 2,5-dimethyl-2,5-di- (t-butyl-peroxy) -hexane, 2,2-bis- (t-butyl-peroxy) -p-diisopropyl-benzene, 1,1-bis- (t-butyl-peroxy) -3,3,5-trimethyl-cyclohexane, 2,5-dimethyl-2,5-di- (t-butyl-peroxy) -hexene-3, di-t-butyl peroxide, benzoyl peroxide, peroxide p-chloro-benzoyl peroxide dicumyl, t-butyl peracetate, perbenzoate t-butyl peroxide monochloro-benzoyl peroxide 2,4-dichloro-benzoyl, and peroxide t-butyl cumyl. The amount of catalyst used will depend on the type of catalyst and can be determined by experimentation. Generally, the catalysts of peroxide are useful in an amount of approximately 0.05 to 10 parts, and more preferably 0.1 to 5 parts by weight of catalyst per 100 parts by weight of ingredient (A).

Another heat cure system that is Applicable is one in which the elastomer composition of curable silicone is cured by crosslinking of polyorgano-siloxane with a crosslinking agent of organo-hydrogen-siloxane in presence of a catalyst containing a metal from the group of platinum. The crosslinking agent of organo-hydrogen-siloxane can contain an average of at least two hydrogen atoms bonded with silicon per molecule, and no more than one hydrogen atom bonded with silicon per silicon atom, satisfying the remaining valences of silicon atoms by atoms of oxygen or by the monovalent hydrocarbon radicals that They comprise from one to seven carbon atoms. The radicals of monovalent hydrocarbon can be, for example, alkyls such as methyl, ethyl, propyl, t-butyl, and hexyl; the cycloalkyl such as cyclohexyl; and aryls like phenyl and tolyl. These materials are well known in the art. The molecular structure of organo-hydrogen-siloxane can be linear, linear including branching, cyclic or net. There are no particular restrictions regarding weight molecular of organo-hydrogen-siloxane, without however, it is preferable that the viscosity at 25 ° C is 3 to 10,000 mPa.s. In addition, the amount of component (C) that is added to the composition is an amount such that the ratio of the number of moles of hydrogen atoms bonded with silicon atoms with with respect to the number of moles of the linked alkenyl groups with silicon atoms, it is in the range of 0.5: 1 to 20: 1; and preferably in the range of 1: 1 to 5: 1. Yes this molar relationship is less than 0.5, the cure of the present composition becomes insufficient, while if this molar ratio exceeds 20, it releases the hydrogen gas so that formation takes place of foam

The catalyst that contains a group metal of platinum can be any catalyst that is known to catalyze the reaction of hydrogen atoms bound with silicon with vinyl groups bonded with silicon. By metal from the platinum group, it is understood as ruthenium, rhodium, palladium, osmium, iridium and platinum. It is preferred that the metal is platinum. The Examples of these platinum catalysts include acid chlorine-platinum, the alcoholic solutions of chloro-platinic acid, acid complexes chlorine-platinum with olefins, the complexes of chloro-platinic acid with the divinyl siloxane, platinum black, platinum metallic, and the catalysts in which the metallic platinum is carried on a stand. The amount of component (D) that is added It varies according to the type of catalyst used, and it is not especially restricted; normally, however, the amount added is 1 to 1,000 parts by weight, preferably 5 to 100 parts by weight of platinum group metal per 1,000,000 parts by weight of component (A).

When the polymer of organo-siloxane is a gum that contains vinyl dimethyl siloxane, preferred that the healing component is selected from the agents of organic peroxide cure. When the polymer of organo-siloxane is a liquid that contains vinyl dimethyl siloxane with a viscosity less than 150,000 mPa.s, it is preferred that the component of healing comprises a crosslinking agent of organo-hydrogen-siloxane and a catalyst containing a platinum group metal.

Optional smoke reducing agents can be added to the ingredients in the composition of the present invention. These smoke reducing agents can be selected at from the materials frequently used in the industry of silicone rubber to reduce fumes, including platinum,  aluminum trihydrate and magnesium oxide. These materials they can help in allowing silicone to pass the criteria of smoke generation As shown below in the examples, the Aluminum trihydrate can have the effect of increasing the heat release of the polymer when burned. Therefore the Aluminum trihydrate should only be used after a experimentation to confirm that the increase in heat shedding is acceptable for the amount of reduction of smoke achieved. On the other hand, the use of platinum in the This composition does not have an adverse impact on the heat shedding, and can be used at levels normally Used for smoke reduction.

Ingredients may optionally include smoke reduction agents, dyes, pigments and others fillers known in the art, including but not limited to, the diatomaceous earth, calcium carbonate titanium dioxide and Mica Among these fillers, diatomaceous earth is preferred. Diatomaceous earth is a common expander filler in rubber silicone. When diatomaceous earth is used, it is preferable add diatomaceous earth as filler in an amount of 10 to 60 percent by weight, based on the total formulation. The land of diatoms in combination with wollastonite changes properties physical such as tensile and elongation of the composition cured

The compositions of the present invention may formulated to pass the UL 910 test for use as overpressure cable material. The UL 910 test is performed on a apparatus known as Steiner's Tunnel. In UL 910 test, cable wires are placed side by side on a tray 0.5 m by 7.6 m in the tunnel with an air flow of 1.22 m / s. The wires are lit at one end with a methane flame of 87.9 kW / m2. The spread of the flame, or distance from the flame paths through the wires, measured after 20 minutes To pass the test, the propagation distance of the flame must be less than 1.5 m beyond the end of the flame of gas. The methane flame is 1.4 m long, and therefore can have a total of 2.9 feet of burned cable of 7.3 m. The maximum optical density of smoke should be less than 0.5 and the value Average must be less than 0.15. The optical density of the smoke is measured in the exhaust duct. The cables must pass the test in two successive cycles to assess the overpressure.

The UL 910 test is expensive in its realization. It requires large amounts of cable and coating material. In addition, it requires a specialized test facility to adapt the dimensions of the test environment. This makes it difficult to test multiple samples. It is understood in the field of fire research that the heat release rate of a product is the most important property that predicts the risks in a fire situation, because it controls the intensity of the fire. It has also been established now that the results of the fire test from the cone calorimeter correlate with those from the natural scale fires. See, for example, Marcelo M. Hirschler, "Comparison of Large- and Small-scale Heat Release Tests with Electrical Cables", Fire and Materials, Vol. 18, 61-87 (1994).

These efforts suggest that an instrument cone calorimeter that measures the shedding speed of the heat, which works with a thermal flow of 88 kilowatts, is a proof that it is useful to select materials in terms of their Ability in overpressure cable sheathing.

In addition to the shedding speeds of heat, it is thought that the formation of a coal structure is important for a material that passes the UL 910 test. When a Typical silicone rubber burns, the carbon structure is Quite fragile and flaky. Thus, if a cable is coated with a typical silicone, carbon can flake or break during calcination, exposing new polymer surfaces for pyrolysis as well as the core material of the cable. If the structure of coal remains hard, there is a possibility that the flame spread be reduced.

Coal can be assessed visually through the amount of cracks, observing if the cracks extend vertically by the sample, by vertical expansion, by change of color and by the amount of visible material not burned. The measurements taken may include weight loss, chemical composition, or expansion height.

Finally, the evolution of smoke is a important component to pass the UL 910 test. As has been set forth above, to pass the Steiner tunnel test, the maximum optical density of the smoke must be less than 0.5 and the Average value must be less than 0.15. The evolution of smoke in the Silicone rubber is typically controlled by the addition of amounts of smoke that contain compounds such as compounds of Platinum, aluminum oxide or magnesium oxide.

Examples Test methods

In the following examples, the heat release rates using a calorimeter of cone. In the cone calorimeter, an electric burner is positioned conical above the sample to emit a defined thermal flux towards the sample. A spark igniter that is located above The surface of the sample is used to ignite the gases volatiles that are distilled from the sample. When the volatiles are light, the time until the ignition is recorded and the igniter by spark stops. The oxygen concentration as a function of time, It is measured to determine the rate of heat release. This is based on the principle that, for most plastics, a constant amount of heat is released by mass unit of oxygen consumed in combustion. This calorimeter is an oxygen consumption calorimeter, ASTM E1354.

Since oxygen concentrations are determine much more easily than heat production in the time, the oxygen depletion calorimeter provides a easy way to determine the heat release rate of the materials.

The dimensions of the samples were 0.10 m x 0.10 m x 6.3 mm and were tested in a configuration horizontal with a metal frame, described in the ASTM, for that the samples cannot curl up. Two were used thermal fluxes of 50 and 88 kW / m2 and were specified in each example. The heat release rate, HRR, which determine the size of a fire, it is calculated from the data of oxygen consumption and distinguishes how much heat is released from the surface area of the sample per unit time.

The samples tested on the cables are spread on a copper wire as insulators. A pair twisted of insulated threads was then coated with a wrap with the same sample to give a thickness of 0.457 mm. The weight of material lining was approximately 1600 grams per linear meter of cable.

Example 1

The elastomer samples were composed to demonstrate the effect of wollastonite on the characteristics fire functionalities of a silicone elastomer net such as model, compared to the functional characteristics of the Fire of silicone elastomers with various fillers. The samples were prepared by using a filler selected from diatomaceous earth, calcium carbonate, aluminum oxide, smoked silica and wollastonite. The amount of Filler in each sample was 10 percent by volume. He Volume percentage is used to ensure that the same volume Silicone rubber fuel is available for each test sample.

The elastomer model network consisted of a dimethyl siloxane terminated by dimethyl vinyl siloxy, with a degree average polymerization (dp) of 434 that was hydroxylated with a polymethyl hydrogen siloxane with its end capped by trimethyl with an average dp of 65, by the use of a platinum catalyst. SiH's relationship with with respect to Si-vinyl it remained constant at 1.5: 1.0 and the amount of Pt was 3 ppm. The samples were made by using a Whip Vacuum Power Mixer Plus Mix® Corporation, Louisville, Kentucky, and cured at 170 ° C for 15 minutes. The samples were then tested in the Cone calorimeter at a thermal flow of 50 kW / m2. The data on the Heat Release Rate (HRR) as a function of time, can be seen in Figure 1.

A control sample was drawn up, carrying the Label Sample 1-6, from the model network of elastomer without padding for comparison with samples with filling. Samples filled with diatomaceous earth, carbonate of calcium and silica showed no significant improvement in HRR, carbon structure or weight loss after combustion with respect to control. The sample with oxide filling of aluminum had a noticeably higher HRR than the sample of control and extremely high weight loss after combustion, which can be seen in Table 1. The elastomer of wollastonite filled silicone had an HRR profile extremely low The material was not foaming and expanding vertically like the other samples, and the weight loss was very low, to 20 percent by weight. This showed that silicone did not had been consumed so quickly in a fire filled with wollastonite as with the control or the other samples with filling.

TABLE 1 Comparison of weight loss after combustion

one

Example 2

Two rubbers of liquid silicone were formulated for overpressure cable coverings. The sample 2-1 contained wollastonite. The sample 2-2 contained diatomaceous earth. Both samples They contained the following: 18.7% by weight of dimethyl siloxane terminated by dimethyl vinyl siloxy with a grade polymerization of 830; 8.8% by weight of dimethyl siloxane terminated by dimethyl vinyl siloxy with a grade polymerization of 434; 16.2% by weight silica dimethyl vinyl and trimethylated; 0.7% by weight of dimethyl, methyl vinyl siloxane, terminated by hydroxyl with an average degree of polymerization of 8; 3.3% by weight of hexamethyl disilazane; 0.2% by weight of water; 9.4% by weight of smoked silica with an area surface area of 250 m 2 / g; 1.9% by weight cerium hydrate; 2.3% by weight of dimethyl terminated by trimethyl siloxy, methyl hydrogen-siloxane, with a average degree of polymerization of 8; 0.06% by weight of 2-methyl-3-butin-2-ol; 0.1% by weight of platinum complexes; and 38.7% by weight of a second inorganic filler, wollastonite or diatomaceous earth. Be jointly mixed the above elements in a mixer Baker Perkins The materials were cured at 150 ° C for 20 minutes and subsequently cured for 4 hours at approximately 200 ° C. Each material was tested in the cone calorimeter at a thermal flow of 88 kW / m2, and HRR data can be seen in Figure 2.

Sample 2-1, filled with wollastonite, had a HRR lower than the Sample 2-2 that had a diatomaceous earth fill. There was also a significant difference in the structures of Coal; the diatomaceous earth filled sample had a fragile, flaky surface that was full of deep cracks, while the sample with wollastonite filling had a coal Hard resinous with some cracks on the surface. The integrity The surface of Sample 2-1 was much higher than the of Sample 2-2.

Example 3

High consistency rubbers were formulated for overpressure cable coverings. The sample 3-1 was made up of the traditional formulation that contains diatomaceous earth as a second inorganic filler in addition of amorphous silica. Sample 3-2 contained wollastonite instead of diatomaceous earth. The sample 3-3 contained a 50/50 mixture of earth from diatoms and wollastonite instead of diatomaceous earth. All the samples contained the following: 16.8% by weight of Base 1; he 16.8% by weight of Base 2; 1.0% by weight of platinum complexes; he 1.0% by weight of peroxide 2,4-dichloro-benzoyl; 0.6% in Base 3 weight; and 60.0% by weight of a second fill inorganic.

Base 1 contained 51% by weight of methyl vinyl dimethyl siloxane finished by dimethyl vinyl siloxy; 19% in weight of amorphous silica with a surface area of 250 m2 / g; he 22% by weight of dimethyl siloxane terminated by hydroxyl; and 3% by weight of phenyl-methyl-siloxane terminated by hydroxyl Base 1 had a plasticity of 1.8 to 1.9 mm.

Base 2 contained 20% by weight silica with a surface area of 250 m 2 / g, treated with vinyl trimethoxy silane and phenyl trimethoxy silane; 11% in methyl vinyl siloxane weight of dimethyl terminated by dimethyl vinyl siloxy; 61% in dimethyl siloxane weight terminated by dimethyl vinyl siloxy; and 4% in weight of dimethyl siloxane terminated by hydroxyl. The Base 2 had a plasticity of 1.4 to 1.5 mm. Base 3 contained the 6% by weight dimethyl siloxane of methyl vinyl finished by α-hydroxyl, ome-methoxy; 25% by weight amorphous silica with a surface area of 250 m2 / g; 19% by weight of methyl vinyl dimethyl siloxane hydroxyl terminated; 48% by weight of dimethyl siloxane terminated by dimethyl vinyl siloxy and 2.5% in weight of several cyclosiloxanes.

All materials were mixed together in a Baker Perkins mixer and cured in a hot press to 150 ° C for 20 minutes. The samples were subsequently cured for 4 hours at 200 ° C. Each sample was tested in the Cone calorimeter at a thermal flow of 88 kW / m2 and the data HRR as a function of time can be seen in Figure 3.

Sample 3-2, sample with wollastonite filling, had a total heat shedding more Low than Sample 3-1, sample with padding of diatomaceous earth. Also, in Sample 3-2, the Carbon structure was hard and resinous without any expansion vertical, the weight loss was only 6% by weight and the fire did not penetrate inside the 1/4 '' thick sample. The sample 3-1 had a flaky coal that was expanding vertically, it cracked and had a 12% weight loss in weight. Thus, there were significant improvements in the sample with wollastonite filling compared to the sample filled with diatomaceous earth. The great peaks of the HRR profile of the Sample 3-3 come from the phenomena of self-extinguishing The cone calorimeter measures the oxygen consumption, and if a sample is self-extinguish and then it re-ignites, there is a big change in the consumption of oxygen that is seen in the HRR profile as peaks. So the mixture to 50/50 of the two fillings proved to be an improvement in functional characteristics of the fire since the material was self-extinguishing now under this great flow hot. Also the coal was similar to the Sample 3-2 and the weight loss was only 8% in weight.

Example 4

The rubbers of great consistency were formulated new for overpressure cable liners with different wollastonite sizes. Sample 4-1 below has a wollastonite with an average particle size of 12 µm and a range of particle sizes of 1-393 µm. Sample 4-2 has a wollastonite with a size average particle size of 10 µm, and a range of sizes of 1-119 µm particles. The formulations are identical to those in Example 3, except that Base 1 and Base 2 have been replaced by Base 4 and Base 5. Base 4 consists of 20% by weight silica with a surface area of 250 m2 / g, 33% by weight dimethyl siloxane of methyl vinyl finished by dimethyl vinyl siloxy, 38% in dimethyl siloxane weight terminated by dimethyl vinyl siloxy, 6% in weight of hydroxyl terminated dimethyl siloxane and 1.2% by weight of cyclosiloxanes that had a plasticity of 63-67. Base 5 is made up of 20% by weight of silica with a surface area of 250 m 2 / g, 50% by weight of methyl vinyl dimethyl siloxane finished by dimethyl vinyl siloxy, 23% in weight of hydroxyl-terminated dimethyl siloxane, a 3% by weight of phenyl methyl siloxane terminated by hydroxyl and 4% by weight of cyclosiloxanes that had a plasticity of 70-73. The materials are mixed in a Baker Perkins mixer and cured in a press heat at 150 ° C for 20 minutes. The samples were cured subsequently for 4 hours at 200 ° C. Each sample underwent test on the cone calorimeter at a thermal flow of 88 kW / m2 and HRR data as a function of time can be seen in Figure Four.

The HRR of samples 4-1 and 4-2 is very similar. There is also none significant difference in the carbon structures of both materials. The difference in average particle size, about 2 µm, it is a small difference.

Example 5

Rubbers of great consistency were formulated for overpressure cable liners with and without complexes of platinum. Platinum is a smoke reducing agent. Formulation of the elastomer was identical to Sample 4-1 except the amount of platinum complexes that changed at 0.0% by weight in the Sample 5-1, and 0.5% by weight in the Sample 5-2. Each sample was tested in the Cone calorimeter at a thermal flow of 50 kW / m2 and the data HRR as a function of time can be seen in Figure 5.

The HRR of Samples 5-1 and 5-2 is very similar. There is also none significant difference in the carbon structures of both materials. Thus, the absence of platinum complexes has an effect significant small about the functional characteristics of the elastomer fire.

Example 6

Elastomer samples were made for demonstrate the effect of wollastonite which is calcium silicate mined compared to a synthetic calcium silicate, Celite C from World Minerals Inc., Lompoc, CA with a surface area of B.E.T. of 175 m2 / g, on the functional characteristics of the Fire of a silicone elastomer model net. The amount of Filler in each sample was 10 percent by volume. He Volume percentage is used to ensure that the same volume of silicone rubber fuel for each sample test.

The elastomer model network consisted of a dimethyl siloxane terminated by dimethyl vinyl siloxy, with a degree average polymerization (dp) of 434 that was hydroxylated with a polymethyl hydrogen siloxane with its end capped by trimethyl with an average dp of 65, by means of use of a platinum catalyst. SiH's relationship with with respect to Si-vinyl it remained constant at 1.5: 1.0 and the amount of Pt was 3 ppm. The samples were made by using Whip Vacuum Power mixer Plus Mix® Corporation, Louisville, Kentucky, and cured at 170 ° C for 15 minutes The samples were then tested in the Cone calorimeter at a thermal flow of 50 kW / m2. The data on the Heat Release Rate (HRR) as a function of time, can be seen in Figure 6. Sample 6-1 Contains a synthetic calcium silicate while the Sample 6-2 contains wollastonite. The sample 6-2 has a heat release rate higher and a 28% higher weight loss compared to 20% The carbon structure of Sample 6-1 is Also quite friable. Thus, wollastonite or calcium silicate mining should be used to intensify the characteristics functional fire elastomer.

Example 7

Rubbers of great consistency were formulated for overpressure cable coverings. The sample 7-1 was made up of the traditional formulation that contains diatomaceous earth as the second inorganic filler and aluminum trihydrate and magnesium oxide as a set of smoke reduction while Sample 7-2 It contained wollastonite as the second inorganic filler. The sample 7-1 contained the following: 17.0% by weight of the Base 4; 17.0% by weight of Base 5; 0.1% by weight of complexes of platinum; 1.0% by weight of peroxide 2,4-dichloro-benzoyl; 0.6% in weight of Base 3; 7.0% by weight of aluminum trihydroxide; a 3.5% by weight magnesium oxide; and 53.8% by weight of land of diatoms Sample 7-2 contained the following: a 18.9% by weight of Base 4; 18.9% by weight of Base 5; 0.1% by weight of platinum complexes; 1.0% by weight of peroxide 2,4-dichloro-benzoyl; 0.6% in weight of Base 3; and 60.5% wollastonite by weight. These materials spread over a bare copper wire of 24 gauge. A pair of lead wires were twisted together and more material was spread to wrap the wire. The weight of silicone coating material on the cable was of approximately 1600 grams per linear meter. These test leads They were tested in the UL 910 tunnel. 7-1 failed in the tunnel while 7-2 passed the UL 910 test requirements for smoke and smoke propagation call.

Claims (9)

1. A silicone composition comprising:

(TO)

of the 30 to 90 percent by weight of a polymer of heat-curable organo-siloxane, which contains at least two alkenyl groups per molecule,

(B)

of the 1 to 65 percent by weight of a reinforcing silica filler, based on the total composition,

(C)

of the 5 to 70 weight percent wollastonite that has a size average of particles of 2 to 30 µm, based on the composition total, and

(D)

a sufficient healing component to cure the composition.

2. The composition according to Claim 1, characterized in that the composition after curing has a maximum heat release of less than 100 kW / m2 when tested at a thermal flow of 50 kW / m2 } 3. The composition according to Claim 1, characterized in that the component (A) is a vinyl-containing polydimethylsiloxane. 4. The composition according to Claim 1, characterized in that the component (D) is selected from the group consisting of 2,5-dimethyl-2,5-di- (t-butyl-peroxy) -hexane, 2,2- bis- (t-butyl-peroxy) -p-diisopropyl-benzene, 1,1-bis- (t-butyl-peroxy) -3,3,5-trimethyl-cyclohexane, 2,5-dimethyl-2,5- di- (t-butyl-peroxy) -hexene-3, di-t-butyl peroxide, benzoyl peroxide, p-chloro-benzoyl peroxide, dicumyl peroxide, t-butyl peracetate, t-butyl perbenzoate, monochloro-benzoyl peroxide, 2,4-dichloro-benzoyl peroxide, and t-butyl-cumyl peroxide. 5. The composition according to Claim 1, characterized in that the component (D) is composed of an organo-hydrogen-siloxane crosslinking agent and a platinum group metal catalyst. 6. The composition according to Claim 1, characterized in that the composition further comprises an effective amount of a smoke reduction agent that is a platinum compound. 7. The composition according to Claim 1, characterized in that the composition further comprises another filler selected from the group consisting of diatomaceous earth, calcium carbonate, titanium dioxide, and mica. 8. A cable for transmission media that comprises a cured silicone rubber coating, prepared by curing a composition formed by the mixture and the cure of:

(TO)

of the 30 to 90 percent by weight of a polymer of non-halogenated, heat-curable polydimethyl-siloxane, which contains at least two alkenyl groups per molecule,

(B)

of the 5 to 25 percent by weight reinforcing silica,

(C)

of the 5 to 70 percent by weight of wollastonite that has a ratio average between dimensions of at least 3 to 1 and an average size of 2 to 25 µm particles, and

(D)

a sufficient healing component to cure the composition.

9. The cable for transmission media according to Claim 8, characterized in that the silicone composition extends with an envelope thickness of 0.2 to 0.6 mm and is capable of passing the UL 910 flammability test.